Theoretical study of the molecular ions SiH?5 and SiH?3 |
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Authors: | Frerich Keil Reinhart Ahlrichs |
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Institution: | Institut für Physikalische Chemie und Elektrochemie, Universitat Karlsruhe, D 7500 Karlsruhe, Germany |
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Abstract: | Ab initio HF and Cl calculations were performed to determine the equilibrium geometry of SiH?5 and SiH?3, the barrier for internal rotation (SiH?5) and inversion (SiH?3) and the stability of SiH?5 and further to study the effect of electron correlation on reaction energies. The gaussian-type basis included d and f functions on Si and a p set on II. The D3h structures of SiH?5 is lower in energy than the C4v structure by 2.9(3.2) kcal/mol (corresponding HF results in parentheses). SiH?3 has C3v structure, the inner-ion barrier computed is 26.2 (27.3) kcal/mol. SiH?5 turns out to be stable with respect to SiH4 + H? by 20.3 (13.8) kcal/mol, but it is unstable with respect to SiH?3 ← H2 by 6.3 (5.6) kcal/mol. These results show that electron correlation has a small effect on barriers of inversion (SiH?3) or pseudorotation (SiH?5), but may have a pronounced effect on reaction energies even if all systems involved have closed shells. The correlation energy contributions are analyzed in terms of intrapair and interpair terms in order to get a better understanding of the influence of correlation on reaction and activation energies. |
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